Method of and apparatus for leveling sheet metal



Nov. 30 1926. 1,608,910

C.G.L.SJ6LANDER METHOD OF AND APPARATUS FOR LEVELING SHEET METAL FiledNov. 22, 1924 Patented Nov. 30, 1926.

UNITED STATES CARL GUSTAF LEONARD SJbLANDER, OF GOTTENBOBG, SWEDEN.

METHOD OF AND APPARATUS FOR LEVELING SHEET METAL.

Application filedgTovember 22,1924, Serial No. 751,645, and in SwedenDecember 6; 1922.

For leveling sheet-metal one generally uses machines with a system ofrollers which bend the sheet two or more times in different directionsand then straighten it in order to remove surface strains and buckles.The said method acts in a rather satisfactory manner on thicksheet-metal and such of a comparatively small breadth, but by thetreatment of sheet-metal having a thickness of up to 2 mm. and when thesame is very broad as for instance 1.5 m. the large buckles only areremoved by the said method. Not only small buckles but also most, of thesurface strains are still remaining and, consequently, the sheet becomeswhat is called waving. This unfavorable result is also caused by therollers deflection or getting warped caused by the pressure during thestraightening operation. Now experience has proved that the thinner thesheet is the smaller must be the diameter of the rollers but, obviously,they will deflect so much the more. Thrust rollers have been employed toprevent such deflection, but in such an arrangement the straighteningrollers are subjected to considerable wear, since the contact surfacebetween the straightening rollers and the supporting rollers isrelatively small. Further, the mechanism becomes complicatedand themaintenance of same On account of the imperfect" expensive.straightening of the sheet it must be subjected to a subsequentstraightening by a hammer either manually or by a machine, which in bothcases is very time-wasting and requires mucli professional skill.

The present invention has for its object to overcome the saidinconveniences, and according to same the straightening operation iseffected in such a manner that, by means of a suitable tool movabletowards and away from the sheet and past which the sheet is parallel;

being fed, the same is curved into a series of undulations extendingalmost perpendicularly to the feed direction of the sheet and the heightof same decreasing successively until they disappear. Thus, buckles andirregular undulations of thesheet are initially transferred into regularwaves whereby the strains in the sheet become more regular or During thecontinued operation the waves are gradually lessened in height,

until they entirely disappear. The tool must work with great speed,'butthe feeding of the sheet which of course is made by steps may proceed byvery short steps. In this manner the sheet will be subjected to a kindof kneading and not even the least unit of area will be left unaffected.

The accompanying drawing shows diagrammatically an apparatus suitablefor the execution-of the above described method.

The tool comprises essentially two parts 1 and 2, the sheet being fedbetween them in the direction of the arrow by means of rollers 16 oranother suitable device. Of said parts the one is movable towards andaway from the other. Both parts are provided with crests 3 to 15 andgrooves respectively, located in such a manner that the crests of onepart correspond to the grooves of the other part. Considering from theentrance side of the tool the crests are at first of decreasing heightand mounted with decreasing mutual distances between them, andthereafter they are equally high and with increasing distances betweenthem in thefeed direction. I

Considered in the feed direction of the sheet the crests 3, 4, 5, 6 havedecreasing height and decreasing mutual distances,

transfer the buckles and undulations into regular waves, then, as thedistance and the height decrease, the sheet will be treated more indetail, and finally when there is no difference in height of crests theimpressed undulations are brought to disappear, provi'ded that the toolis properly adjusted-referring to the drawing, so adjusted that thecrests 6, 13, 7 slightly strike the opposite surfaces of the leveledsheet, whereupon the sheet passes straight between the remaining crests14, 8, 15 which. merely execute a slight pressure on the sheet.

The increasing mutual distances of the crests 6, 7 8 and 12, 13, 14', 15has the purpose of makingthe adjustment of the tool The last mentionedcrests may caused by the tool will not exactly corre;

elasticity of the sheet-metal.

easier and to neutralize the effects of small differences of thicknesswhich may occur in the sheet.

The said neutralizing is partly due to the Because of this elasticitythe deformation of the sheet remaining height of the bends each timebeing diminished dueto the increasing distances between the crests andto the elastic-- ity of the sheet-metal. At a certain point theelasticity will have neutralized the undesired bends caused by theincreased thickness of the sheet. In this way the tool adjustment willbe less critical with a greater number of tool crests with equal heightand with gradually increasing mutual distances than with fewer crests ofthis kind.

In general the number of crests, their heights and mutual distances haveto be chosen to suit the thickness of the sheet to be leveled.Experience has proven that the thinner the sheet is the more severe mustbe the treatment in order to remove the original buckles and. strains.Therefore it will be suitable to provide a tool for leveling thin sheetswith a greater plurality of crests and arrange them closer together thanby a tool fpr thicker sheets, not precluding that different thicknesseswithin certain limits may be treated using one and the same tool.

The tool has to be mounted in. a suitable press which may work withgreat speed for example two hundred to five hundred strokes a minute or,it may be, with still greater speed, in order to make this'method mosteconomical. As the movable tool part need not move mbre than 1.5 to 4mm. towards and away from the other part the speed of the mac ine may beconsiderably raised.

The feeding of the sheet has to take place during that period of'thestroke when the movable part of the tool is withdrawn a little distancefrom the other part thereby letting the sheet free. The sheet is movedforward one step to each stroke of the press,

and the length of the step may not be greater than 1 to 3 times thethickness of the sheet, as the tool otherwise will leave undulations inthe sheet, assuredly only some hundredth or some hundredths mm. high.Presuming the press to make 500 strokes a minute and the feed to be 2mm. a stroke, the

feeding speed will make 1 m. a minute or 60 m. an hour, which provesthat the straightening operation proceeds very rapidly.

Having now described my invention, what I claim as new and .desire tosecure by Letters Patent is v 1. A method of leveling sheet metalconsisting in feeding a sheet of metal in a substantially straight line,intermittently ex.- erting pressure on the opposite sides of the sheetsto form a series of undulations, suc cessively decreasing the height andlength of the undulations in the direction of feed of the metal sheet,and finally exerting pres sure'on the sheet to flatten out and eliminatethe undulations.

2. An apparatus for leveling sheet metal comprising sheet feeding means,two cooperating parts each having a plurality of crests and grooves, thecrests of one part corresponding with and opposing the grooves of theother part and adapted, upon reciprocation of said parts to formundulations in a sheet of metal interposed therebetween, the distancebetween the crests and the distance of the crests of each part from thefed sheet decreasing in the direction of feed of the sheet metal, saidcooperating parts also having opposing portions equidistant from the fedsheet adapted to press out the undulations in the metal sheet andflatten the latter.

In witness whereof, I have hereunto signed my name.

CARL GUSTAF LEONARD SJtlLANDI-IR.

